1. Technical Field
The present invention relates to a substrate used for an electro-optical device, such as a liquid crystal display device. Further, the invention relates to an electro-optical device, such as a liquid crystal display device, and to an electronic apparatus including the same.
2. Related Art
Electro-optical devices, such as liquid crystal display devices, have come into widespread use for electronic apparatuses, such as a mobile phone and a personal digital assistant. For instance, the electro-optical device has been used as a display device for displaying various information items related to the electronic apparatus. The electro-optical device is for controlling an optical output by means of an electrical input, and for example, includes a liquid crystal display device, an EL (electroluminescent) device, a plasma display device, and so forth.
For example, in the liquid crystal display device, a pair of substrates are provided with electrodes, respectively, and a liquid crystal layer composed of an electro-optical material is interposed between the electrodes. A voltage applied to the electrodes is controlled, which causes the alignment of liquid crystal molecules in the liquid crystal layer to be controlled, so that light incident on the liquid crystal layer is modulated by the alignment control. The pair of electrodes overlap each other in a plurality of dot regions that are arranged in the longitudinal and transverse directions. These dot regions constitute display dot regions, which are display units. When color display is carried out by three primary colors of blue, green, and red, a set of three display dot regions corresponding to these three colors constitutes one pixel. Meanwhile, when monochromatic display is carried out by white and black, or two arbitrary colors, one display dot region constitutes one pixel.
In general, in order to increase display contrast, a light-shielding layer is formed around the display dot regions. In the related art, there has been known a technique in which the light-shielding layer is formed by laminating any two colored layers of a plurality of colored layers, for example, three colored layers of blue, green, and red (for example, see Japanese Unexamined Patent Application Publication No. 10-073813 (page 3 and FIG. 1). In this manner, when the light-shielding layer is fabricated by laminating colored layers having different colors, the colored layers having different colors are laminated at the same position with the same width by a photolithography method, and are then patterned.
In the photolithography method, a resist film is formed on a colored-layer forming material to be patterned, and is then exposed through an exposing mask by an exposure apparatus. As the exposure apparatus, for example, a stepper or a batch exposure apparatus is used. At the time of the exposure process, when patterning is performed after one colored layer is laminated on another colored layer, a positioning process, i.e., an alignment process is performed between these colored layers.
When this alignment process is exactly performed, a desired light-shielding layer is formed, and thus color display having a desired color property is obtained. However, in the currently performed alignment process, it is difficult to completely remove misalignment when the colored layers are laminated. The use of the stepper as the exposure apparatus makes it possible to reduce the degree of the misalignment to a minimum, as compared to when using the batch exposure apparatus, but it is still difficult to completely remove the misalignment.
When the misalignment occurs between the laminated colored layers, one colored layer projects from an edge portion of the light-shielding layer. As a result, the entire base color of display is greatly affected by the color of the projecting colored layer. Further, when the misalignment occurs between the colored layers, color irregularity occurs due to the color of the colored layer projecting from the edge of the light-shielding layer. As a result, a variation in the entire base color of display occurs between a plurality of manufactured liquid crystal display devices.